Studies of timing and magnitude of sea-level changes during MIS 5 derived from Barbados coral reef terraces - a critical review and new results
In: Journal of Coastal Research, Jg. SI (2005) ; Nr. 42, S. 52-62
Zeitschriftenaufsatz / Fach: Geowissenschaften
Rektorat und Verwaltung » Rektorat
This paper presents a historical overview of the dating of MIS 5 coral reef terraces and palaeo sea level studies on Barbados. Additionally, new morphological and geochronological investigations conducted on Barbados between 1990 and 2003 are summarized. Reef stages from the last interglacial transgression maximum (MIS 5e) are located at 20 m to 50 m asl on Barbados. Assuming that these reef stages record the same sea level highstand, uplift rates must have varied spatially and, most probably, temporally. Some localities, such as the region east of South Point (southern Barbados), are not suited for palaeo sea-level estimates because they have experienced differentiated tectonic uplift. In contrast, the reef terraces preserved to the east of the Christ Church standard traverse are not affected by the Christ Church anticline. Their reef crests maintain a constant elevation above present sea level in the area to the west of South Point and may be used for palaeo sea-level reconstruction. The transgression maximum of MIS 5e is documented by two sea-level maxima; MIS 5e-3 (T-5b) and MIS 5e-2 (T-5a), which are approx. 132,000 yrs and 128,000 yrs old, respectively. This indicates, that the last interglacial sea level highstand most likely lasted a few thousand years only. After that, sea level dropped and reached approx. -13/-8 ± 2 m asl during MIS 5e-1 (T-4) approx. 118,000 yrs ago. Three coral reef terraces T-3, T-2, and T-1b were formed on the south coast of Barbados during the last interglacial sub-stage MIS 5c around 105,000 yrs. The chronostratigraphy of these various MIS 5c coral reef terraces can not yet be differentiated—neither by the abundant ESR data nor by the relatively few U/Th data. For the first time, a double sea level oscillation and the associated formation of two morphologically distinct coral reefs (T-1a₁ and T-1a₂) was recognized on Barbados for MIS 5a. Both reef terraces were identified and mapped on the south coast of Barbados. ESR dating sites yielded ages of approx. 74,000 yrs for T-1a₁ and approx. 85,000 yrs for T-1a₂.